A great diversity of genetic regulatory mechanisms exist and it is important that they be investigated in a number of different systems. The y region of bacteriophage lambda is a prototype of a fundamentally different control system from the classical operon model of Jacob and Monod. In the lambda y region, control is achieved by modulating the amount of transcription through a termination site. This type of control system is used elsewhere in bacteriophage lambda, in the E. coli trp operon, in the S. typhimurium his operon, possibly in the E. coli ilv operon, and may be used in many other systems. The lambda y region is the only system in which point mutants affecting the termination process have been isolated. The y region is ideal for investigation from both a genetic and a biochemical perspective. Recently the nucleotide sequence of the entire y region has been determined by Dr. Martin Rosenberg at the National Cancer Institute. He is now determining sequence changes of mutants in the y region, most of which were isolated and characterized in my laboratory. This is revolutionizing our understanding of transcriptional control in the y region and suggesting new genetic and biochemical experiments. My first objective is to continue the basic genetic studies which underlie all investigations of the y region. To this end, I propose to continue to isolate and characterize mutants in the y region, and to construct more strains which are useful for probing the function of this region. I also plan to continue my collaboration with those doing sequencing and transcriptional studies. Finally, by investigating the rates at which the lambda repressor is synthesized in infections by various lambda mutants, I hope to better understand how transcription is regulated in this region.